The dispensing of an ophthalmic lens which meets the individual requirements of a wearer is an important factor in determining wearer satisfaction.
Whilst it is relatively common for lens dispensers to consider very basic requirements of a wearer (for example, prescription) and to dispense a lens according to the these types of requirements, such an approach is quite limited. Consequently, although by using such an approach a lens design may be dispensed which has a suitable prescription, the lens may have other features which render the lens unsuitable for the individual needs of the wearer.
Moreover, in recent years the availability of a large number of different lens designs has complicated the dispensing process, and thus rendered the dispensing process more difficult. Indeed, a good example of the difficulty faced by dispensing lenses having a complex design is progressive addition lens.
Conventional progressive addition lenses are one-piece lenses which have an upper distance portion (‘the distance zone’), a lower near portion (‘the near zone’), and a progressive corridor (‘the intermediate zone’) therebetween which provides a gradual power progression from the distance zone to the near zone without any dividing line or prismatic jump.
Although early progressive lenses were somewhat crude in design, they have consistently improved in performance over the past few decades. The improvement in performance has been a causative factor in significantly increasing patient demand for these categories of lenses to the point where lens dispensers and manufacturers today offer an array of different progressive lens designs. There is thus available to a dispenser a large number of lens designs that may be dispensed to a wearer, each of which would be suitable to meet that wearer's prescription requirements.
The provision of a range of progressive lens designs presents a lens dispenser with something of a dilemma. The dilemma lies in the fact that in increasing the number of different lens designs which are available to be dispensed to a particular wearer, there is an associated increase in the complexity of the decision making process involved in selecting a lens design which is best suited to the wearer's individual needs.
The selection of a particular lens design from the array of available lens designs for an individual wearer, and the subsequent fitting of the selected lens design to a frame to form spectacles for use by the wearer, are of critical importance to the effectiveness of, and thus the wearer satisfaction with, the resultant spectacles.
Ideally, the process of selecting a progressive lens design for an individual wearer includes selecting a lens design having a power distribution which is ‘matched’ to an individual wearer's needs. In this respect, the power distribution of a progressive addition lens may be described in terms of a number of design parameters. Examples of design parameters which may be relevant include:    (a) the length of the power progression;    (b) the shape of the progressive corridor;    (c) size, shape and location of the near, intermediate and distance zones;    (d) blur gradients across boundaries of peripheral zones;    (e) specific aspherisation of the near and distance zones; and    (f) the design of peripheral zones.
In light of the number of design parameters which may be varied, selecting a progressive addition lens which is suitable for a wearer's individual needs is a matter of making trade offs. For example, increasing the size of the near zone may improve the near viewing performance, but may have a corresponding degrading effect on the distance viewing performance and active vision performance by increasing the levels of blur and distortion elsewhere in the lens.
Unfortunately, given the large array of PAL products on the market and the almost infinite combinations and permutations of the design parameters, and the variety of tasks for which a lens may be used, selecting a lens design (from a dispensers perspective) or designing a lens (from a designers perspective) which is suitable for an individual wearer's needs has proven to be somewhat difficult. Therefore, when selecting a progressive lens for a wearer, many dispensers miss the opportunity to fit a lens which has been selected on the basis of the wearer's needs because they instead fit a favorite, trusted lens design.
If a dispenser does attempt to custom fit a progressive lens design, they are often limited by their experience, design knowledge which they have personally developed and/or data supplied by a lens manufacturer. Such limitations may have negative consequences for the consistency of the dispensing process between different retail locations or within retail locations where several dispensers may work. Thus, the same wearer may be offered very different lens design solutions. In this scenario, then, the lens design offered to a customer may depend on:    (a) which dispenser a customer consults with;    (b) a dispensers experience and prejudices;    (c) sales targets of the store;    (d) the number of designs that a dispenser can hold in memory; and    (e) the type of information the manufacturer has supplied on which to make dispensing decisions.
Different wearers, though, typically have different lens usage requirements, some of which may be related to the wearer's lifestyle (for example, a wearer's vocational and avocational activities). Different vocational and avocational activities may encompass different ranges of accommodative demands due to, for example, variation in the working distance requirements of the activity and the nature and relative motion of the visual targets associated with the activity. Thus, different activities may warrant different considerations in the selection of an appropriate lens design.
To accommodate such variations, some lens designs have been developed specifically for particular activities (for example, for computer users who have high intermediate vision demand coupled with high near vision demands). However, providing a lens design which is optimised for a particular activity (for example, reading) is often detrimental to the vision performance for other tasks which the wearer performs.
As a result, many dispensers prescribe single vision lenses for such activities as golf or tennis in preference to a progressive addition lens. Although such an approach may provide a lens design which is suitable for a particular activity, it may force the wearer to wear different spectacles for activities having different working distances (for example, one set of spectacles for reading and another for playing golf).
It is an aim of the present invention to provide a method and a system that can be used on-site by a dispenser, at least to select or design a suitable lens design, such as a progressive addition lens design, based upon lifestyle and/or other information provided by the wearer, preferably in a reasonably short period of time.